Cox, B.M. & Sumbler, M.G. 2002. British Middle Jurassic Stratigraphy. Geological Conservation Review Series, No. 26, JNCC, Peterborough, ISBN 1 86107 479 4.
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K.N. Page
Hackness Rock Pit (sometimes known as Ilackness Quarry') is a small disused quarry sited on the south side of the road alongside Lowdales Beck, north-west of Hackness Hall, c. 7.5 km west of Scarborough, North Yorkshire. It is the type locality of the Hackness Rock Member of the Osgodby Formation and the last significant exposure within the area in which William Smith first recognized and mapped the 'Hackness Rock' (Smith, 1829, 1832; Sheppard, 1917)
The following description is based on Wright (1968) with additional observations by K.N. Page. The succession in the upper part of the section is now unclear because of deep weathering and vegetation.
| Thickness (m) | |
| Osgodby Formation | |
| Hackness Rock Member | |
| 6: Limestone with berthierine ooids, flaggy; poorly preserved Quenstedtoceras | 0.30 |
| 5: Sandstone, dark-greenish, somewhat flaggy; berthierine ooids, calcareous in part; band with common Euaspidoceras hirsutum (Bayle) associated with Quenstedtoceras ex gr. lamberti (J. Sowerby) in upper part; otherwise rich fauna dominated by Q. ex gr. lamberti with rarer Grossouvria sp., Hecticoceras (Putealiceras) cf. puteale (Leckenby), Kosmoceras (K.) ex gr. spinosum (J. de C. Sowerby), Peltoceras (Peltomorphites) subtense (Bean) and bivalves including Chlamys | 0.23 |
| 4: Sandstone with berthierine ooids and calcareous concretions; richly fossiliferous with Kosmoceras (Lobokosmokeras) ex gr. proniae Teisseyre and K. (K.) ex gr. spinosum (J. de C. Sowerby), less common Grossouvria (G.) sulcifera (Oppel) and Hecticoceras spp., and rare Binatisphinctes hamulatus (S.S. Buckman), Chamoussetia funifera (Phillips) and Longaeviceras; bivalves including Chlamys, Gryphaea lituola Lamarck and Pleuromya; rhynchonellid and terebratulid brachiopods; small corals | 0.15 |
| 1–3: Sandstone, pale to orange-coloured, calcareous, flaggy in part; few ammonites including Kosmoceras (L.) proniae and Peltoceras sp. | 1.33 |
| Langdale Member | |
| Sandstone, massive, fine-grained | c. 4.9 |
The ammonite faunas of beds 1–3, including forms previously described as Kosmoceras bigoti (Douvillé) and K. rimosum (Quenstedt), indicate the Proniae Subzone of the Upper Callovian Athleta Zone. Most of the ammonites indicative of this zone at Hackness Rock Pit, some of which have been figured by Callomon and Wright (1989) and Cox (1988), have come from the overlying Bed 4. As here understood, Kosmoceras (L.) ex gr. proniae includes macroconch and microconch forms including those previously described as K. (L.)duncani (J. Sowerby), K. rimosum and K. rowlstonense S.S. Buckman non Young and Bird. K. (K.) ex gr. spinosum possibly includes forms previously described as K. (K.)bigoti (Douvillé), K. (K.) compressum (Quenstedt) and K. (K.) aff. transitorius (Nikitin), and the Hecticoceras spp. includes macroconch and microconch forms previously ascribed to H. (Sublunuloceras) and H. (Brightia) respectively. The Pseudocadoceras boreale S.S. Buckman recorded by Wright (1968) is possibly a microconch Longaeviceras. According to Callomon and Wright (1989), the holotype of Chamoussetia funifera (Phillips) came from the Athleta Zone of either Hackness Rock Pit (i.e. Bed 4 or below) or Scarborough. Many of the ammonites in Bed 4 are fragmentary, which suggests some reworking; a mixture of both Proniae and Spinosum Subzone forms appears to be present. According to Wright (1968), there is no evidence to support Arkell's (1939b) statement that the Hackness Rock extends down into the Coronatum Zone.
The ammonite fauna of Bed 5 is typical of the lamberti Biohorizon (Upper Callovian Lamberti Zone and Subzone). Callomon and Wright (1989) indicated that the type locality of Quenstedtoceras flexicostatum (Phillips), a microconch of Q. lamberti, could be Hackness Rock Pit or Scarborough but, as the preservation of the specimen is good, Hackness Rock Pit is the more likely. However, it should be noted that since the quarry that forms the GCR site is not marked on William Smith's map made in 1829 or 1830 (Sheppard, 1917), there must be some doubt about it being the source of specimens described by Phillips (1829).
Loose specimens of Cardioceras (Scarburgiceras) aff. scarburgense (Young and Bird) indicative of the Lower Oxfordian Mariae Zone, have been found in rubble in Hackness Rock Pit, having been washed down from the Oxford Clay Formation above Bed 6 (Wright, 1968). This suggests that excavations at the site might reveal a good Callovian–Oxfordian stage boundary section (Wright, 1968).
As type locality of the Hackness Rock Member of the Osgodby Formation, Hackness Rock Pit is an important lithostratigraphical reference section.
The sequence of ammonite faunas here is also of significance; it is virtually the only remaining site where good Athleta Zone faunas can be collected in situ in the region and it also appears to show a sequence of Lamberti Subzone faunas. Indeed, further sampling may well reveal new stratigraphical information of international correlative significance including data on the Callovian–Oxfordian stage boundary.